Looking for the most simple solution. Bring your wisdom

[Truckinthumper]

I am full time mobile in a toyhauler turned office. Just me.
I have a generator and dont mind using it, just want to turn it off at night.
I have been monitoring my actual usage through a Kill-o-meter and an app with my shore power surge protector.
At any given time I am drawing 400 watts, occasional jumps to 550 (fridge?), and can run around 450 for a few seconds(Keurig?).
My Microwave uses about 800 for a few minutes a day.
The Kuerig brings me 2 or 3 cups of attitude adjust each morning. 1700 watts on brew.
I dont use the toaster very often, but it sucks up about 800 watts for a few minutes.
I am not too concerned with the A/C for this project, if it is that hot, I will fire up the genny.
I do run the electric "fireplace" on occasion. 1500 watts when running. Again, if need be, I can run the genny.
I dont plan on being in cold or too hot of a place for very long. Why I am mobile.

This is my power audit.

What I want:
Enough battery to run 400watts, for 8-10 hour minimum at night, that is the least I want.
Ideally, to run the above power requirements for 24 hours, if I have sun and panels. Or run the entire gig for 1 day with no sun or generator.
If I have a day two of rain, I will fire up the genny.

The build:
I have all sorts of space on the roof for panels. The location for all the batteries and such will have to be in the "garage", as living area storage is not really there.
Which is good, as I planning an area for that already.

The wiring:
This got me thinking. Rather than run a bunch of wires to the converter area, why not just run a 50 amp cable to the backside of the 50 connection?
I can get to it very easily and running the cable would be a stupid simple task.
Since I am a bit ignorant of electricity, If the all in one, or solar generator can put out 25 or so amps of AC, why not, that is what the RV is designed for.
So, would a rack mount(48v 200ah) and all in one make my life easy?
I can swing two of the rack mounts if need be.

 

[RoadTurtle]

Simpliest solution, put in an inverter (min 2000-2200), and attach it to a 50a plug and just plug into your trailer, when you need 120v power off of batteries. You will have to add a disconnect or figure out how to turn off your charger/converter. Given some of the loads you have, you need to be able to handle the current flow and probably looking at a minimum of 2 100ah LITHIUM batteries or 1 larger unit. Lead acid or AGM don't handle high current loads well. I did this and it worked awesome... but, it wasn't quite enough for true off grid camping. I now have the victron Multiplus II 2x x 120v and absolutely love it. Yes it's pricey, but my 5th wheel has 120v power full time, even when stored.

 

[50ShadesOfDirt]

As a thought exercise, I did the following for you:

1. used your numbers above, at a typical "solar design calculator" site:
https://unboundsolar.com/solar-information/offgrid-calculator (helps you determine energy audit stuff)
- just use one appliance at 400w for 8 hrs/day, and get "system size" in watt-hours
- this site helps you nail down all appliance calcs

2. go to another website, where they help you turn watt-hours into generic components:
https://www.altestore.com/store/calculators/off_grid_calculator/
- plugging in 3200wh, at 48v reference voltage, yields 1000w of panels, 200aH of batteries, 48v inverter, etc
- keep tweaking various inputs, and you'll see the changes on outputs

Now that you have "numbers" for everything, you can have those kinds of websites send you quotes & details; these are somewhat useless in my mind, because they want to sell you stuff. You'll never know if you are getting good stuff for all your requirements and constraints, or stuff that just happens to be in their inventory that they need to move.

So, armed with the above numbers, such as a system reference voltage of 48v, now go look at Will Prowse's typical designs for off-grid systems (what your RV is), and find one that fits your numbers. You now have a reference design, complete with diagrams, details, etc.

3. click on this forum's link for "DIY Solar Products and System Schematics", and start reviewing information to nail down what works for you.

When I did all of this for you (in about 15m or so), I came up with:
- 48v system reference voltage ... yielded smallest battery bank size
- two solar panels for 1000w ...
- 200aH LiFePO4 battery bank ... smallest arrangement of batteries

Who knows if this will work for you, better than you doing it yourself? Run through all of the above and see if it gets you where you need to be on your learning journey. No substitute for wading in there and figuring stuff out ...

Hope this helps ...

 

[12VoltInstalls]

Simpliest solution, put in an inverter (min 2000-2200), and attach it to a 50a plug and just plug into your trailer, when you need 120v power off of batteries.

That is really a great solution imho.

Rather than run a bunch of wires to the converter area, why not just run a 50 amp cable to the backside of the 50 connection?

You can do that, but you’ll need to incorporate a transfer switch.

But if you’re using an AIO, you could merely run the shorepower cable to a junction box and feed direct to the aio as they have a built in transfer switch, and have pass-through current features. Essentially you’re replacing the oem onboard converter with the aio, bypassing and disabling the oem converter. Then you don’t have to assure you’re not mixing power sources ever (because that will provide disheartening results).

If the all in one, or solar generator can put out 25 or so amps of AC, why not

What about the native lighting? Water pump? Furnace fan? Leveling jacks? Bath vent fan? Range hood fan?
Though less so in recent years, most RVs do all the above with 12VDC. A 48V system would require you to provide for the 12V services somehow. I might suggest sticking with a 12V battery bank for your max intermittent high draw is the fireplace, coffeemaker, and microwave- and those are within range of the maximum wattage practical for 12V. The battery cabling will be a bit more money (for 2/0) but not Porsche-to-Camry different.

location for all the batteries and such will have to be in the "garage"

Being close to the battery bank will make cabling costs less to absorb.

the all in one, or solar generator can put out 25 or so amps of AC, why not

I wouldn’t even consider a ‘solar generator.’ Twice the money and not as long-term dependable, plus half the power/$.

A single 3000W Victron Multiplus may not run the A/C with other loads needing some of the bandwidth. Most if not all other 3000W AIOs will be 24V or 48V and we’re back to the beginning.

 

[Rocketman]

I full-time in an RV. (ClassA)

The 400w load 24/7 seems REALLY REALLY high or is that just for daylight hours?

400w for 24 hours is 9.6kwh which is over double my useage. I use just under 5kwh/day.
Do you have an absorption fridge that is on electric??? If so consider changing it out for a compressor fridge (residential), The change out will pay for itself in batteries.

I highly recommend Victron., the information you get becomes priceless. A Multiplus 3000 - will run any one large item (toaster, microwave, hair dryer, coffee maker or even air conditioner (with a soft start)

For reference this is my system
Multiplus 12/3000
Solar 1400w it is overpanel end - mppt 1140w capacity.
540ah 12v diy lithium battery.
Smartshunt
GX device - get the Cerbo (I have the older CCGX).

This runs is just fine unless we are in trees or bad weather - then the generator needed exercise anyway… the only I don’t use on inverter is the water heater and second air conditioner.

(The air conditioner can only be ran for an hour).

If your electric demand is that high you will need twice the battery and twice the solar as me.
So 2000 to 3000 w of solar
Lithium Battery -
12v - 1000ah
24v - 500ah
48v - 250ah

Good Luck!

 

[RoadTurtle]

The 50A power cord is 120VAC at 25A each leg. The A/C system might care about that. A single 3000W Victron Multiplus may not run the A/C with other loads needing some of the bandwidth. Most if not all other 3000W AIOs will be 24V or 48V and we’re back to the beginning.

Incorrect, a 50a trailer is actually 50a on EACH leg, for a total of 100a. Look at the circuit breakers, there are two breakers, each one is listed at 50a.

Also Multiplus is 3000VA, not 3000w, distinct difference.

 

[time2roll]

Yes two of those 48 x 200 batteries are needed. The additional equipment will increase the base draw. The Victron should run one A/C or other large item without issue. All the small stuff can run together. Looks like 6 large panels may get up there just fine. Maybe more. Could start with 4 and see what goes.

 

[12VoltInstalls]

Incorrect, a 50a trailer is actually 50a on EACH leg, for a total of 100a. Look at the circuit breakers, there are two breakers, each one is listed at 50a

Thank you. I need to proofread myself when just blasting out responses without thinking. My mind’s been on running 240V for my TiG through a 10ga cord; my head was stuck in 30A mode I guess. No idea. (I need 50A, but I have a dbl 30 breaker and I’m unwilling to spent $350 on a 8ga cord when I have 150’ of 10ga)

 

[RoadTurtle]

Thank you. I need to proofread myself when just blasting out responses without thinking. My mind’s been on running 240V for my TiG through a 10ga cord; my head was stuck in 30A mode I guess. No idea. (I need 50A, but I have a dbl 30 breaker and I’m unwilling to spent $350 on a 8ga cord when I have 150’ of 10ga)

I have seen self proclaimed licensed electricians, and even one master electrician make the statement it's only 25 amps per leg. In fact the master electrician, was calling me all kinds of names and I was causing people to burn their trailers down. The irony, he admitted a 50a trailer was good for 12,000 watts, but I couldn't get him back to 50a per leg. His cognitive dissonance just couldn't make that jump to 100a total.

 

[Vigo]

Call me crazy but OP said he is willing to buy 20kwh of battery (2x 48v 200ah) and as far as im concerned, that means the answers to all other questions are ‘yes’ because those batteries will be the most expensive part of the entire build, and can easily support a 24hr period of no solar/gen/shore power unless he pulls out all the stops and runs both ACs for a long period.

At the point that you’re talking about spending 20kwh of lithium money it’s silly to talk about the limitations of a 3000va inverter, let’s talk 5-10kw inverters instead. Nobody puts a 20 gallon gas tank on their riding mower..

@Truckinthumper I hope this is encouraging to you.. noone has said anything not true, but given your roof real estate, battery budget, mild consumption habits.. to me this is sounding pretty easy!

 

[12VoltInstalls]

make the statement it's only 25 amps per leg

Maybe it’s the W=V(A) thing that crosses brain cells? Because I have a 30A dbl breaker which is neither 25A nor 50A and I knew a double 30A breaker might still nuisance trip- so exactly why I wrote that about 25A who knows?

 

[Zack R]

When doing your power audit with the kill a watt on the 120VAC side you are also measuring the battery charger and possibly the refrigerator. If you have an absorption refrigerator it will use something like 300-400W for heating when plugged in, but only 10-20W on propane only.

I'd do a separate power audit on the DC side (unplugged from 120VAC) to really see what is going on. The Victron Smart shunt is a handy tool for doing this kind of power audit and can be incorporated permanently into the system once you build it.